She soon felt "herself" again. Mother had high blood pressure and insomnia, yet this drink didn’t raise her blood pressure one bit. Nor did it keep her awake at night. In fact, it helped her relax more and sleep a bit better. The drink I suggested was green tea.

Green tea contains much less caffeine than coffee — 15 mg a cup compared with 80-100 mg in coffee. More importantly, it contains high levels of an amino acid called l-theanine, and l-theanine counteracts some of the negative effects of caffeine.

Caffeine is a double-edged sword. It has beneficial qualities, like helping burn fat faster, and boosting both mental and physical performance. But it also increases anxiety and can contribute to high blood pressure in people with hypertension. A number of people find they can’t drink caffeinated drinks after noon because it keeps them from getting a good night's sleep. But green tea seems to be the exception to this rule, unless you're exceptionally sensitive. It can give you the positive qualities of caffeine — like mental alertness — along with the benefits of l-theanine.

L-theanine's actions
L-theanine increases the production of dopamine and serotonin, two brain chemicals associated with alertness, pleasure, and a good mood. Around half an hour after drinking a cup of green tea, you may notice that you feel calmer. This is because the l-theanine increases alpha waves — the very same relaxing brain waves that are produced during meditation.

At the same time, its mild stimulating effect can wake you up. Green tea is a perfect beverage for a pick-me-up afternoon break. It can restore your mental alertness and calm you down from the day’s pressures at the same time.

Studies found that l-theanine significantly reduces blood pressure in hypertensive animals. The more they were given, the more their blood pressure dropped. How can this be possible if tea also contains caffeine? In addition to its ability to make relaxing alpha waves, l-theanine seems to cancel out some of the jittery effects of caffeine.

The amount of l-theanine in a cup of green tea varies from 15-30 mg. Here’s why. The tea plant converts this amino acid into antioxidants when tea leaves are exposed to sunlight. So the longer the leaves remain on the tea plant, the lower the theanine levels. This explains why young, more expensive green teas will contain higher amounts of l-theanine than less expensive varieties.

If you don’t like green tea, or if you want to take higher levels of l-theanine than you can get in a drink, there are always supplements. Try taking 200 mg from one to three times a day. It could make you feel more relaxed and alert than the tea itself.

Personally, I always prefer using whole foods or herbs whenever possible. They contain co-factors, such as beneficial antioxidants. Use supplements only if drinking a few cups of green tea per day doesn’t give you the results you’re looking for or you just plain don’t like it. You can, of course, combine green tea with other herb teas, such as peppermint and ginger, to mask its taste.

If you thought that green tea’s caffeine would keep you up at night, now you know it probably won’t. Besides, you can always drink decaffeinated green tea. It's still high in l-theanine. Just look for good quality teas, such as those from Traditional Medicinals or The Republic of Tea. You can find these and other quality teas in most health food stores and in some supermarkets.

Huber, Luke G., ND. "Green tea catechins and l-theanine in integrative cancer care," Alternative & Complementary Therapies December 2003.

Juneja, L.R., et al. "L-theanine – a unique amino acid of green tea and its relaxation effect in humans," Trends in Food Science and Technology, June 1999.

L-theanine: Monograph, Alternative Medicine Review, vol. 10, no. 2, 2005.

Yokogoshi, Hidehiko, et al. "Effect of theanine, r-glutamylethylamide, on brain monoamines and striatal dopamine release in conscious rats," Neurochemical Research, May 1998.